Past experience will lead to fundamental physical and psychological changes in our perception and reaction to future events. When we experience terrifying things, we store experience memories so that we can recall them when we encounter similar situations. We are naturally designed to Achievement is to stay away from harmful stimuli and avoid unfavorable encounters, but when we cannot control and prevent these reactions, they will begin to interfere with our normal reactions.
If a person has experienced the stimulus brought about by a specific situation, and felt the fear or pain in it, he will try to avoid this situation in the future to avoid behavioral reactions and prevent himself from being hurt. From the perspective of human evolution, one of the well-known examples is the fear of snakes. This fear is considered to be the survival response of some people and is passed down from ancestors. This inference is reasonable because it allows us to see When snakes do not try to take risks, so as to ensure that we can keep our lives and continue to develop.
Like most processes in the brain, fear is a complex process that involves different cells and structural parts, leading to our behaviors and physiological responses. Maintaining internal balance is the key to the normal functioning of the human body. However, when the balance changes, such as overexpressing the fear response in the wrong environment, it will lead to dysfunction and in many cases develop into chronic mood disorders and anxiety disorders. We can usually observe this phenomenon in patients with post-traumatic stress syndrome (PTSD) because they are no longer able to distinguish the clues as threatening and show overreaction to conditions that were previously considered harmless.
In order to prevent us from being paralyzed by fear under unnecessary circumstances, which poses a threat to our health and ability to respond correctly, we have the opposite mechanism to discern what may be a real threat to us and those that are not to us. There is a threat. We can learn and forget the response to certain cues. This ability belongs to the field of neuroplasticity—that is, our ability to adapt to the environment and adjust our physiology to make it adapt to and cooperate with the stimuli of the real environment.
This cellular response in the brain is related to the epigenetic mechanism. Chemical tags will be added to the DNA in the neurons in the brain responsible for the fear-related behavioral response area. The purpose is to achieve a balance between the various stimuli that people can learn from and respond to. , Will not overexpress them in the wrong context. To achieve this goal, "forget" harmful reactions will work.
Understanding what may be regarded as dangerous to us will induce epigenetic modifications, turn on or turn off certain genes to adjust our response to different situations. People have known for a long time that certain chemical labels will cause dangerous stimuli Fear responses, such as 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5mhC), are more active in neurons than other cells because they respond to the learning process.
Animal studies have also shown that these epigenetic modifications appear differently in males and females, triggering different processes to perceive fear. In the research conducted by Dr. Sase and his team on mice, they found that an epigenetic tag has a specific role in females, such as suppressing memories caused by fear, while activating the same tag in males does not cause this effect. This kind of label seems to be more likely to weaken the fear-related memory in female memories. This is due to the fact that the arrangement and positioning of epigenetic labels is different from that of males, while male labels are not weakened or changed in similar situations. This found It reveals how a variety of factors change people’s perception of fear experiences, such as gender.
Dr. Li Xiang and his researchers recently published another important study in Nature Neuroscience. They discovered the existence of another kind of epigenetic signature, which we did not know before was related to the process of fear overcoming. The process of overcoming fear is contrary to the formation of fear memory and regulating our response to it. It is a two-way system and the opposite way. The overcoming of fear depends on gene expression in various regions of the brain, especially from the prefrontal cortex of the lower limbs ( ILPFC) gene expression, which can ensure that we can overcome potentially harmful fear responses in the wrong situation.
After exploring the function of this system, scientists can better understand the neural mechanisms that occur in emotional learning and memory, and how fear-related memories are reversed. Scientists have discovered that the epigenetic label N6-methyl-2'-deoxyadenosine (m6dA) is necessary for the correct overcoming of fear memory, because it can activate the gene for overcoming fear. The researchers studied this by placing the mouse in a box, and after emitting a specific audio, a slight electric shock was delivered to the mouse. This caused the mice to associate this tone with an electric shock, so that they remained still when they heard the tone. In order to allow it to overcome the recent formation of memories related to fear, the researchers placed the mouse in a new box, where the audio was played repeatedly without electric shock. After that, the rats were immediately returned to the original box, where they no longer exhibited fear behavior of the tone.
However, in order to further explore the cellular components involved in this process, they examined the DNA of mouse neurons and found that m6dA tags did appear in most regions of the entire genome. The label is highly concentrated on the gene of brain-derived neurotrophic factor, which is related to the process of learning and storing memory. In the process of overcoming fear, the m6dA tag seems to increase the activity of this gene. This study reveals that it is not only important to explore how epigenetic signatures change between cell populations, but it also reflects how they change in environmental-related events, such as overcoming fear-related memories and re-adjusting our learning. .
These epigenetic mechanisms are crucial to understanding how debilitating diseases (such as PTSD or anxiety disorders) develop. Combining our understanding of these mechanisms with more suitable therapies is important for finding tools to dismantle such systems. , And preventing such diseases from disrupting our normal functions will be invaluable. Memories related to fear are essential for noticing and responding to dangerous situations. When the system is out of adjustment and we are no longer able to recognize situations that may cause danger, we cannot react normally and are limited. Therefore, mastering all the factors that help overcome fear is essential for developing appropriate treatments.